1. Field of Invention
The invention relates generally to substrate support assemblies and methods for supporting and stabilizing a substrate within a machine that performs an operation on the substrate, and more particularly to a substrate adjustment assembly of a stencil printer particularly designed to adjust the position of the substrate during a print operation.
2. Discussion of Related Art
In a typical surface-mount circuit board manufacturing operation, a stencil printer is used to print solder paste onto a printed circuit board. A circuit board, broadly referred to as an electronic substrate, having a pattern of pads or some other conductive surface onto which solder paste will be deposited, is automatically fed into the stencil printer. One or more small holes or marks on the circuit board, called fiducials, is used to align the circuit board with the stencil or screen of the stencil printer prior to the printing of solder paste onto the circuit board. The fiducials serve as reference points when aligning a circuit board to the stencil. Once a circuit board has been aligned with the stencil in the printer, the circuit board is raised to the stencil by a substrate support, e.g., a table having pins, and fixed with respect to the stencil. Solder paste is then dispensed onto the stencil, and a wiper blade or squeegee traverses the stencil to force the solder paste through apertures formed in the stencil and onto the board. As the squeegee is moved across the stencil, the solder paste tends to roll in front of the blade, which desirably causes mixing and shearing of the solder paste so as to attain a desired viscosity to facilitate filling of the apertures in the screen or stencil. The solder paste is typically dispensed onto the stencil from a standard cartridge. After the print operation, the board is then released, lowered away from the stencil, and transported to another station within the printed circuit board fabrication line.
As referenced above, the stencil and the circuit board are aligned to accurately print solder paste precisely on the pads of the circuit board. In one known stencil printer, the substrate support is connected to spring-loaded actuators to control the x-axis movement, the y-axis movement and the theta or rotational movement of the substrate support. To achieve alignment of the substrate and the stencil, the spring-loaded actuators are manipulated to control the movement of the substrate support.